[ti:Can and Be Able To] [by:www.51voa.com] [00:00.00]更多听力请访问51VOA.COM [00:-1.00]Modal verbs are helping verbs. [00:03.97]We use them with main verbs to help us express ability, [00:09.87]possibility, necessity and permission. [00:14.49]Today's question is about a modal [00:17.50]that is commonly confused with an expression. [00:21.78]Here's the question, which comes from a listener named Cafer: [00:28.08]Hi! Would you like to explain the difference [00:31.34]between "can" and "be able to"? [00:34.53]Thank you. -Cafer [00:36.25]Hi, Cafer! [00:38.03]I can explain the differences between the two. [00:41.82]I just used "can" to talk about my ability to do something. [00:47.25]We also use "be able to" for abilities, [00:50.86]but usually only when "can" is not possible. [00:55.45]I'll tell you what that means in a minute. [00:58.61]But first, let's explore the word "can." [01:02.01]"Can" is a modal verb. We use it to: [01:06.84]talk about present or future ability or possibility [01:11.88]I can play the guitar. [01:13.79]You can buy the tickets online. [01:17.60]You must use "could" for the past tense, such as in, [01:23.46]"You could have bought the tickets online." [01:26.62]We also use "can" to: [01:29.26]ask for or give permission [01:33.46]I am finished. Can I go now? [01:35.42]Yes, you can. [01:37.22]and to ask someone to do something [01:41.51]Can you bring me the magazine? [01:44.28]Now, let's explore "be able to." [01:48.09]This expression is not a modal. [01:50.96]It is the verb "to be" plus the adjective "able." [01:56.55]The word "to" shows that an infinitive verb will follow. [02:02.51]We use "be able to": [02:05.28]when it is not possible to use "can" for abilities, [02:09.33]such as after other modal verbs [02:13.45]I won't be able to take you to the train station. Sorry! [02:17.48]You should be able to finish the book in a few days. [02:22.18]The words "won't", short for "will not", [02:26.49]and "should" are modals. [02:29.08]In English, we do not put two modals together. [02:33.15]So, we cannot put "can" after them. [02:38.06]We also use "be able to": [02:41.35]to talk about small or large past successes. [02:45.77]We were able to get a great price on the television. [02:49.90]She was able to win the math competition last month. [02:55.09]But in negative form, we can use "be able to" or "could": [03:02.23]We couldn't get a great price on the television. [03:06.43]She wasn't able to win the math competition last month. [03:11.60]But note that the negatives "wasn't able to" [03:15.34]and "weren't able to" are a little more formal than "couldn't." [03:20.35]And that's Ask a Teacher. [03:22.39]I'm Alice Bryant. [03:24.40]更多听力请访问51VOA.COM